Howdo I know what to look for.....

In the search for a new bass, how do I know what to look for and want. I mean how do I know that it feels the best and sounds the best. I don't have the luxury of playing many other different basses cause everyone seems to have a Squier around here. I may be able to check out my teachers... but thats about it. I am pretty sure I want a Jazz bass cause it will give me a better sound range. But what do I look for when i pick up and play a different bass? The strings, how the neck feels, do i like how its balanced. That sort of thing.